Water plasticized high refractive index polymer for ophthalmic applications

ABSTRACT

A high refractive index, foldable polymer suitable for use in ophthalmic devices, such as intraocular lenses, is provided. The polymer may be produced from a polymerization reaction of first, second and third monomeric components and a crosslinking agent. The first monomeric component includes an aryl acrylate or an aryl methacrylate. The second monomeric component, which is not an acrylate, includes a monomer having an aromatic ring with a substituent having at least one site of ethylenic unsaturation. The third monomeric component includes a high water content hydrogel-forming monomer. The resulting high refractive index copolymer is durable enough to be cut and polished when dry, and becomes soft and foldable when hydrated.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to the Apr. 12, 1999 filing dateof provisional application Ser. No. 60/128,751.

BACKGROUND OF INVENTION

[0002] This invention relates to copolymer materials which are useful asophthalmic devices, such as contact lenses, intraocular lenses (IOLs),keratoprostheses, and corneal rings or inlays, and a process for makingand using such copolymer materials. In particular, this inventionrelates to intraocular foldable lenses formed from acrylic copolymermaterials.

[0003] With recent advances in small-incision cataract surgery,increased emphasis has been placed on developing soft, foldablematerials suitable for use in artificial ophthalmic lenses. In general,these materials fall into one of three categories: hydrogels, silicones,and generally, others.

[0004] The refractive power of a lens is a function of its shape and therefractive index of the material of which it is made. A lens made from amaterial having a higher refractive index can be thinner and provide thesame refractive power as a lens made from a material having a relativelylower refractive index. Thinner lenses are easier to insert and causeless trauma during surgery.

[0005] Hydrogel materials are hard or rigid when dry, and absorb a largeamount of water (e.g., up to 20-70% by weight) when hydrated, whichlowers the refractive index of the material. These materials tend to bebrittle when dry, and have poor mechanical properties for ophthalmicapplications. In a hydrated state, hydrogel materials become soft andpliable. Known hydrated hydrogels have a relatively low refractiveindex, for example, less than 1.48. In addition to adversely affectingthe refractive index, the absorbed water also significantly increasesthe diameter and thickness of the IOLs, for example, by as much as about15 percent.

[0006] Silicone materials have a slightly higher refractive index (forexample, 1.51), but tend to unfold too rapidly after being placed in theeye in a folded configuration. The biocompatibility of siliconematerials may also be a concern.

[0007] U.S. Pat. No. 5,290,892 (Namdaran et al.), U.S. Pat. No.5,331.073 (Weinschenk, III et al.), and U.S. Pat. No. 5,693,095 (Freemanet at.), the complete disclosures of which are hereby incorporated byreference, discuss forming foldable lenses out of a polymer materialderived from an ethoxyaryl (meth)acrylate with a crosslinker or with asecond acrylate monomer and crosslinker. Since the polymer material issoft/foldable, those patents discuss mold forming the polymer materialto individually form the lens. Likewise, U.S. Pat. No. 5,433,746 toNamdaran et al., which is herein fully incorporated by reference,discloses forming flexible intraocular lenses by molding polymericmaterials which have a relatively low glass transition temperature. Suchmolding requires specialized equipment and expensive customized molds.In addition, the resulting molded lenses tend to have poor surfacequality since they generally cannot be polished. Alternatively, U.S.Pat. No. 5,331,073 discusses forming lenses from a soft foldablematerial by machining the lenses at cryogenic temperatures. Such aprocess is cumbersome and expensive.

[0008] A foldable, high refractive index material, which may be machinedand polished using conventional technology, would be a significantadvancement in the art.

SUMMARY OF THE INVENTION

[0009] The present invention provides a foldable, high refractive indexmaterial which may be machined using inexpensive conventional lathecutting techniques, such as those used in the manufacture of polymethylmethacrylate (PMMA) lenses. The polymeric materials are useful forforming ophthalmic devices, particularly intraocular lenses, comprisingpolymer units derived from at least three different monomericcomponents. The resulting polymeric materials are also useful for otherophthalmic devices, such as contact lenses, keratoprostheses,intracorneal lenses (ICL), and corneal rings or inlays, as well as forother applications.

[0010] A significant novel aspect of polymeric material of the inventionis that it both (a) is hard enough to machine at room temperature, and(b) may be rendered foldable through a controlled hydrating process.Further, the IOL may be hydrated to a suitably flexible state withminimal water uptake. The relatively low water uptake allows efficienthydration without affecting mechanical or optical properties and withoutchanging the dimensions or the refractive index of the foldable lens.Another major advantage of the invention is the ability to tumble polishthe lenses to provide smooth and rounded edges. This is facilitated, inpart, by the relatively high glass transition temperature (Tg) of thematerial.

[0011] One aspect of the present invention is a composition comprising ahydratable copolymer. The copolymer includes:

[0012] a) a first monomeric component which is an aryl acrylate or anaryl methacrylate;

[0013] b) a second monomeric component which is a monomer having anaromatic ring with a substituent having at least one site of ethylenicunsaturation, wherein the second monomeric component is other than anacrylate; and

[0014] c) a third monomeric component which is a high water contenthydrogel-forming monomer. Preferably, the copolymer further includes acrosslinking agent.

[0015] Another aspect of the invention is an ophthalmic device made fromthe copolymer of the invention.

[0016] The invention also provides a process for making ophthalmicdevices such as intraocular lenses from the polymer(s) disclosed. Theprocess generally involves forming a rigid polymer work piece from thecopolymer of the invention, forming an ophthalmic device from the workpiece, and hydrating the ophthalmic device to a sufficiently soft andflexible state so that, if desired, the device can be folded.

[0017] A further aspect of the invention is a method of implanting anophthalmic device within an eye. The method involves providing ahydratable ophthalmic device which is rigid at room temperature whendry, and foldable at room temperature when hydrated. The ophthalmicdevice is hydrated and a syringe is provided which contains the hydratedophthalmic device. The ophthalmic device is then injected into the eye.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The polymer material of the present invention comprises polymerunits derived from the polymerization of first, second, and thirdmonomeric components. These components may include aryl (meth)acrylatemonomer, an aromatic monomer, and a high water content hydrogel-formingmonomer, respectively. Preferably a crosslinking agent is included. Eachof the components is described below in more detail.

[0019] The composition may optionally include other monomericcomponents, an initiator, or an ultraviolet (UV) absorbing material. Theproportions of the monomers should preferably be chosen to produce asubstantially rigid polymer having a glass transition temperature of atleast about normal room temperature. Each of the three differentmonomeric components is preferably present in the copolymer in an amountof at least about 10 weight percent, more preferably, at least about 20weight percent. This invention contemplates preparation of random andblock copolymers of the monomeric components discussed herein. Unlessotherwise stated, all weight percents are based on the total weight ofthe composition prior to polymerization.

[0020] In a highly preferred embodiment, the composition comprises ahydratable copolymer which includes:

[0021] a) at least about 20 weight percent of a first monomericcomponent such as ethylene glycol phenyl ether acrylate or polyethyleneglycol phenyl ether acrylate;

[0022] b) at least about 10 weight percent of a second monomericcomponent such as styrene or substituted styrene;

[0023] c) at least about 10 weight percent of a third monomericcomponent such as hydroxy ethyl methacrylate, hydroxyethoxy ethylmethacrylate, or methacrylic acid; and

[0024] d) less than about 10 weight percent of a crosslinking agent suchas a diacrylate or a dimethacrylate. The resulting copolymer has arefractive index greater than about 1.50 and is foldable at normal roomtemperature (that is, about 20-25° C.) when hydrated.

Monomers

[0025] Generally, the first monomeric component is an aryl acrylate oran aryl methacrylate. These compounds may also be referred to as aryl(meth)acrylate monomers. The term “aryl” implies that the compoundcontains at least one aromatic group. Such compounds typicallycorrespond to the formula (I):

[0026] where:

[0027] Z is —H or —CH₃, and

[0028] Q includes at least one aromatic ring.

[0029] Representative substituents Q include, without limitation:ethylene glycol phenyl ether, poly(ethylene glycol phenyl etheracrylate), phenyl, 2-ethylphenoxy, 2-ethylphenoxy, hexylphenoxy,hexylphenoxy, benzyl, 2-phenylethyl, 4-methylphenyl, 4-methylbenzyl,2-2-methyphenylethyl, 2-3-methylphenylethyl methacrylate,2-4-methylphenylethyl, 2-(4-propylphenyl)ethyl,2-(4-(1-methylethyl)pheny)ethyl, 2-(4-methoxyphenyl)ethyl,2-(4-cyclohexylpheny)ethyl, 2-(2-chlorophenyl)ethyl,2-(3-chlorophenyl)ethyl, 2-(4-chlorophenyl)ethyl,2-(4-bromophenyl)ethyl, 2-(3-phenylphenyl)ethyl.2-(4-phenylphenyl)ethyl), 2-(4-benzylphenyl)ethyl and the like.

[0030] Suitable aryl (meth)acrylate monomers include, for example:ethylene glycol phenyl ether acrylate (EGPEA), poly(ethylene glycolphenyl ether acrylate) (polyEGPEA), phenyl methacrylate, 2-ethylphenoxymethacrylate, 2-ethylphenoxy acrylate, hexylphenoxy methacrylate,hexylphenoxy acrylate, benzyl methacrylate, 2-phenylethyl methacrylate,4-methylphenyl methacrylate, 4-methylbenzyl methacrylate,2-2-methyphenylethyl methacrylate, 2-3-methylphenylethyl methacrylate.2-4-methylphenylethyl methacrylate, 2-(4-propylphenyl)ethylmethacrylate, 2-(4-(1-methylethyl)pheny)ethyl methacrylate,2-(4-methoxyphenyl)ethylmethacrylate, 2-(4-cyclohexylpheny)ethylmethacrylate, 2-(2-chlorophenyl)ethyl methacrylate,2-(3-chlorophenyl)ethyl methacrylate, 2-(4-chlorophenyl)ethylmethacrylate, 2-(4-bromophenyl)ethyl methacrylate,2-(3-phenylphenyl)ethyl methacrylate, 2-(4-phenylphenyl)ethylmethacrylate), 2-(4-benzylphenyl)ethyl methacrylate, and the like,including the corresponding methacrylates and acrylates, and includingmix thereof. Other aryl acrylate monomers and aryl methacrylate monomersare likely to occur to one skilled in this art in light of the presentdisclosure. EGPEA and polyEGPEA are preferred.

[0031] The first monomeric component should be added to the compositionin an amount sufficient to provide high refractive index, a moderatewater uptake, and enhanced backbone rigidity. Preferably, the firstmonomeric component comprises at least about 10 weight percent of thecomposition; more preferably, at least about 20 weight percent; mostpreferably, at least about 30 weight percent. The first monomericcomponent should be added in an amount to avoid an undesirably low glasstransition temperature in the resulting copolymer. Preferably, the firstmonomeric component comprises less than about 60 weight percent of thecomposition; more preferably, less than about 50 weight percent; mostpreferably, less than about 45 weight percent.

[0032] The second monomeric component includes a monomer having anaromatic ring with a substituent having at least one site of ethylenicunsaturation. Preferably, this second monomeric component is not anacrylate. Such monomers correspond to the general formula (II):

[0033] where X is —H or —CH₃, and Ar is a substituted or unsubstitutedaromatic ring.

[0034] Representative second monomeric components include, for example,substituted and unsubstituted styrene compounds. These compounds may besubstituted with hydrogen, halogen (e.g. Br, Cl, F), lower alkyl groups(e.g. methyl, ethyl, propyl, butyl, isopropyl), and/or lower alkoxygroups. Monomers containing acrylic or acrylamide bridges should beavoided. Suitable aromatic monomers include, for example: styrene,methoxy styrene, and chlorostyrene. Styrene and chlorostyrene arepreferred. Styrene is most preferred.

[0035] The second monomeric component should be added in an amountsufficient to increase the glass transition temperature of the resultingcopolymer to a desired working temperature. The second monomericcomponent is believed to provide a higher refractive index via thearomatic ring, hydrophobocity, and a higher glass transitiontemperature. Preferably, the second monomeric component comprises atleast about 10 weight percent of the composition; more preferably, atleast about 15 weight percent; most preferably, at least about 20 weightpercent. The second monomeric component should be added in an amountless than that at which the refractive index, optical clarity, or otherdesirable properties of the copolymer are adversely affected.Preferably, the second monomeric component comprises less than about 60weight percent of the composition; more preferably, less than about 40weight percent; most preferably, less than about 30 weight percent.

[0036] The third monomeric component comprises a high water contenthydrogel-forming monomer. Preferably, the third monomeric componentincludes a methacrylate without an aromatic substituent. Suitable highwater content hydrogel-forming monomers include, for example:hydroxyethyl methacrylate (HEMA), hydroxyetboxyethyl methacrylate(HEEMA), hydroxydiethoxyethyl methacrylate, methoxyethyl methacrylate,methoxyethoxyethyl methacrylate, methoxydiethoxyethyl methacrylate,ethylene glycol dimethacrylate, n-vinyl-2-pyrrolidone, methacrylic acid,vinyl acetate and the like and mixtures thereof. One skilled in this artwill recognize that many other high water content hydrogel-formingmonomers are likely to be operable in view of this disclosure. HEMA andHEEMA are preferred.

[0037] The third monomeric component is desirably added in an amountsufficient to render the resulting copolymer hydratable. Preferably, thethird monomeric component comprises at least about 10 weight percent ofthe composition; more preferably, at least about 20 weight percent; mostpreferably, at least about 25 weight percent. The third monomericcomponent should be added in an amount low enough to avoid statisticallysignificant expansion upon hydrating the copolymer. Preferably, thethird monomeric component comprises less than about 60 weight percent ofthe composition; more preferably, less than about 50 weight percent;most preferably, less than about 40 weight percent.

[0038] The copolymer may also include a crosslinking agent. Thecopolymerizable crosslinking agent(s) useful in forming the copolymericmaterial of the invention include any terminally ethylenicallyunsaturated compound having more than one unsaturated group. Preferably,the crosslinking agent includes a diacrylate or a dimethacrylate. Thecrosslinking agent may also include compounds having at least two(meth)acrylate and/or vinyl groups. Particularly preferred crosslinkingagents include diacrylate compounds represented by the following formula(III):

[0039] wherein X′ and X″ separately and independently represent ahydrogen atom or a methyl group; and A represents a substituted orunsubstituted divalent hydrocarbyl group. In a preferred form of formula(III), A represents a substituted or unsubstituted divalent aliphaticradical, and preferably a 1-6 carbon alkylene.

[0040] Representative crosslinking agents include, for example:diacrylate compounds including ethylene glycol dimethacrylate (EGDM),diethylene glycol dimethacrylate, polyethylene glycol dimethacrylate,alkyl methacrylate, 1-3-propanedioldimethacrylate allymethacrylate,1,6-hexanediol dimethacrylate, 1,3-butanediol dimethacrylate,1,4-butanediol dimethacrylate as well as, divinyl compounds includingdivinyl hydrocarbons and divinyl benzene, and the like. Ethylene glycoldimethacrylate is preferred.

[0041] The crosslinking agent should be added in an amount sufficient topermit the hydrated copolymer to return to its original shape afterbeing folded. Preferably, the crosslinking agent comprises at leastabout 1 weight percent of the composition; more preferably, at leastabout 3 weight percent. Conversely, the crosslinking agent should beadded in an amount low enough avoid making the copolymer too rigid orbrittle. Preferably, the crosslinking agent comprises less than about 10weight percent of the composition, more preferably, less than about 5weight percent.

[0042] One skilled in the art will appreciate that additives such asultraviolet (UV) blocking agents, colorants, etc. optionally may beadded to the polymer of this invention depending upon the intendedapplication. Representative UV absorbing materials include thosedisclosed, for example, in column 5, lines 3-29 of U.S. Pat. No.5,433,746 to Namdaran et al., which is herein incorporated by reference.Suitable UV absorbers include, for example, benzophenone, vinylbenzophenone, and benzotriazole. When employed, the UV absorbingmaterial is preferably added in a concentration less than about 1percent based on the total weight of the composition.

[0043] The copolymers of the invention may be produced usingconventional polymerization techniques. For example, the monomers can beblended together and heated to an elevated temperature to facilitate thepolymerization reaction. Catalysts and/or initiators, for example,selected from materials well know for such use in the polymerizationart, may be included in the monomer mix in order to promote, and/orincrease the rate of, the polymerization reaction. Representativeinitiators include free radical initiators such as2-2′-azobisisobutyronitrile (AIBN), benzoyl peroxide, acetyl peroxide,lauryl peroxide, t-butyl peroxide, and the like and mixtures thereof.2-2′-azobisisobutyronitrile (AIBN) is preferred.

Method

[0044] Turning now to the method of manufacturing ophthalmic devicesfrom the copolymer, the method entails the following general steps. Arigid, hydratable copolymer is provided which is derived from a mixtureof first, second, and third monomeric components as described herein.The copolymer has a glass transition temperature greater than aboutnormal room temperature, and has a refractive index greater than about1.55. The rigid copolymer is then formed into a rigid ophthalmic devicehaving the desired dimensions. The copolymer is then hydrated to form afoldable hydrated ophthalmic device. Preferably, the hydrated copolymerhas an equilibrium water concentration less than about 10 weightpercent, and a refractive index greater than about 1.55.

[0045] More specifically, the copolymer of the present invention istypically formed in the shape of sheet or rod. A rigid ophthalmic deviceis generally formed by cutting the device, such as from a rigid sheet ofthe copolymer, and polishing the device. The ophthalmic devices of thedesired dimension and diopter may be cut from the rigid copolymer sheetusing customary lathe cutting techniques at room temperature. Similarly,the devices can be polished using customary polishing techniques, suchas tumble polishing. The ophthalmic device is preferably an IOL.

[0046] The resulting ophthalmic device is then hydrated. This may beachieved by soaking the ophthalmic device in an aqueous solution (suchas water or saline), preferably at an elevated temperature (e.g. between20-100° C.), for sufficient time to inculcate the device with water(e.g. for a time period of from several minutes to several hours orlonger).

[0047] An ophthalmic or other device fabricated from a polymer of thepresent invention does not significantly expand or change shape whenhydrated. In other words, there is no statistically significantdifference between the diameter and thickness of the dry device and thatof the hydrated device. Thus, for IOLs, the rigid intraocular lens andthe foldable hydrated intraocular lens have essentially the samedimensions.

Copolymer Properties

[0048] The copolymers of the invention have a unique combination ofdesirable characteristics, for example, high refractive index, goodmechanical properties, high glass transition temperature, opticalclarity, hydratability, and foldability once hydrated.

[0049] A particularly advantageous combination of properties includeshaving a copolymer which is foldable at room temperature despite havinga glass transition temperature above room temperature, and which alsohas a refractive index (RI) greater than about 1.50. Because therefractive index of the hydrated copolymer tends to be greater than 1.50(and the preferred copolymers have a refractive index greater than about1.55), the copolymers are especially attractive for ophthalmicapplications such as intraocular lenses. The refractive power of a lensis a function of its shape and the refractive index of the material ofwhich it is made. A lens made from a material having a higher refractiveindex can be thinner and provide the same refractive power as a lensmade from a material having a relatively lower refractive index. Thinnerlenses are easier to insert and cause less trauma during surgery. Thus,in general, the higher the refractive index, the better the materialwith other factors remaining the same. RIs of at least 1.558 have beenattained.

[0050] The mechanical properties of the copolymer, such as the glasstransition temperature, permit it to be cut and polished (i.e.,machined) at room temperature (rather than molded, or shaped atcryogenic temperatures). The copolymer is rigid at normal roomtemperature when dry, and flexible at normal room temperature whenhydrated. In other words, the dry copolymer is rigid or solid enough atroom temperature to be workable by conventional cutting or lathing; andthe hydrated copolymer is flexible enough at room temperature that itcan bend 180 degrees without cracking. Beneficially, the dry copolymeris also not very brittle.

[0051] The ability to cut and polish an ophthalmic device facilitatesforming a lens having the minimum central thickness allowed by therefractive index of the material. Thus, a thinner lens is obtainablefrom the copolymer of the invention than from material having the samerefractive index that must be molded. For example, a 20 diopter lens maybe produced having a central thickness less than about 0.4 mm. Thethinness in turn permits the copolymer to be injected through anincision as thin as about 1 mm or less. This provides a significantadvancement in the field of ophthalmic surgery in which much largerincisions are customary.

[0052] Regarding the glass transition temperature (Tg) of the copolymer,the Tg is preferably greater than about normal room temperature so thatit is workable by conventional cutting and lathing techniques.Preferably, the Tg is greater than about 20° C., more preferably greaterthan about 25° C., and most preferably, greater than about 30° C.Suitable ophthalmic devices made of copolymers having glass transitiontemperatures greater than about normal body temperature may also beobtained. Differential scanning calorimetry (DSC) provides a method ofmeasuring Tg.

[0053] As discussed, the copolymer of the invention becomes flexiblewhen hydrated. The hydrating process allows a highly efficientdistribution of water molecules throughout the structure of the IOLs tomake the hard polymer soft and foldable with minimal water uptake. Thehydrated copolymer has an equilibrium water content (EWC) less thanabout 10 weight percent. Preferably, the EWC is less than about 8% byweight, more preferably less than about 5%, and most preferably, lessthan about 4% by weight. Such low water uptake allows efficienthydration without adversely affecting mechanical or optical propertiesof the foldable lens. For example, neither lens dimensions norrefractive index change significantly upon hydration. Regardingexpansion upon hydration, the copolymers of the invention tend to expandless than about 10 volume percent when compared to the unhydratedcopolymer; preferably, the volume percent expansion upon hydration isless than about 5%. Expansion percent is calculated by measuring thedifference in dimension of standard buttons before and after hydration.

[0054] Thus, the copolymer of the invention exhibits a desirable andunique combination of properties including machinability whenunhydrated, and minimal expansion upon hydration; the copolymer also hasa relatively high refractive index.

Surgical Method

[0055] Employing the copolymer of the invention, cataract surgery may becarried out through an incision of 1.5 mm or less. After applyingtopical anesthesia to the eye, an IOL made of the new copolymer materialmay be injected into the eye. No sutures are necessary in this process.

[0056] A method of implanting an ophthalmic device within an eye may becarried out by providing a hydratable ophthalmic device which is rigidat room temperature when dry, and foldable at room temperature whenhydrated. The ophthalmic device is hydrated and a syringe is providedwhich contains the hydrated ophthalmic device. The ophthalmic device,which is preferably an intraocular lens made of the copolymer of theinvention, is then injected into the eye. Desirably, the ophthalmicdevice is injected into the eye through an incision less than about 1.5mm in length.

[0057] The lens may be inserted using a device, for example, like thatdescribed in U.S. Pat. No. 4,715,373 to Mazzocco, which is herein fullyincorporated by reference. The shape or fixation system used to positionthe IOL in the eye is not critical to this invention. The copolymers maybe used in a foldable lens having a variety of fixation systems. See,for example, U.S. Pat. No. 5,776,191 to Mazzocco, which is herein fullyincorporated by reference, for a discussion regarding fixation systemsfor IOL structures.

EXAMPLES Example 1

[0058] Various copolymers are prepared by mixing the followingingredients under reduced pressure: a first, second and third monomericcomponent, a crosslinker and a polymerizable UV blocking agent. Vinylbenzotriazole at a total concentration of 0.3% by weight is utilized asthe UV blocking agent. To initiate polymerization a free radicalinitiator 2-2′-azobisisobutyronitrile (AIBN) is employed atconcentration of 0.2% by weight. The monomer solution is mixed in aglass flask using a magnetic stir bar for 30 minutes. The solution isthen filtered through a 0.2 micron (μ) filter and injected into a sheetmold comprising two glass plates held together with spring clips andseparated by a plastic gasket. The mold is then placed in a water bathfor 10 hours at 60° C., then removed and post cured at 95° C. in ovenfor 12 hours. A clear, bard polymer sheet is obtained.

[0059] Intraocular lenses of various diopters (5, 10, 20, and 34) arecut from the rigid plastic sheet using conventional machining techniquesas used to manufacture polymethylmethacrylate (PMMA) IOLs.

[0060] The IOLs are tumble polished for 2 days at 20° C. The polishedlenses are rinsed with ultra-pure water. At this stage the IOLs arestill hard and non-foldable. The IOLs are then placed in individualvials filled with saline solution. The vials are placed in a temperaturecontrolled oven and subjected to the following conditioning cycle:increase temperature from 20° C. to 40° C. at a rate of 10 degree C perhour. Hold at 40° C. for 30 minutes. Increase temperature from 40° C. to60° C. at a rate of 10 degree C per hour. Hold at 60° C. for 4 hours.Decrease temperature from 60° C. to room temperature (approximately 20°C.) at 10 degree C per hour. The IOLs were soft and easily foldable andhad excellent optical properties. Lens dimensions (optic size,thickness, diameter) did not change significantly with hydration. Thesurface and edges of the samples were found to be very smooth.

[0061] The equilibrium water content was measured after hydration usinggravimetric analysis. The refractive index and glass transitiontemperature of the lenses was also measured. The results are shown inTable 1. TABLE 1 EWC Formula- 1st 2nd 3rd Cross- (Weight Machin- Fold-RI Expansion tion Monomer Monomer Monomer linker %) ability ability(hydrated) % 1 40% 26% 30% 4% 4 Good Fair 1.551 1.5 EGPEA styrene HEMAEGDM 2 35% 26% 35% 4% 3.8 Good Fair 1.551 1.5 EGPEA styrene HEEMA EGDM 340% 20% 36% 4% 3.5 Fair Poor 1.552 1.3 poly chloro- HEMA EGDM EGPEAstyrene 4 43% 26% 27% 4% 4.1 Good Fair 1.551 1.8 EGPEA styrene meth-EGDM acrylic acid 5 25% 11% 60% 4% 12.1 Fair Fair 1.523 5.8 poly styreneHEMA EGDM EGPEA 6 40% 26% 30% 4% 4.0 Good Good 1.551 0.1 poly styreneHEMA EGDM EGPEA 7 45% 31% 20% 4% 1.3 Good Poor 1.556 0.1 poly styreneHEMA EGDM EGPEA 8 50% 36% 10% 4% 1.1 Good Poor 1.554 0.1 poly styreneHEMA EGDM EGPEA 9 25% 11% 60% 4% 16.5 Poor Fair 1.509 7.2 poly styreneHEEMA EGDM EGPEA 10 40% 26% 30% 4% 9.2 Poor Fair 1.514 6.5 poly styreneHEEMA EGDM EGPEA 11 45% 31% 20% 4% 4.6 Poor Fair 1.533 2.3 poly styreneHEEMA EGDM EGPEA 12 50% 36% 10% 4% 5.3 Poor Fair 1.541 3.6 poly styreneHEEMA EGDM EGPEA 13 40% 28% 30% 2% 5.1 Fair Good 1.551 0.3 poly styreneHEMA EGDM EGPEA 14 34% 31% 32% 3% 5.0 Fair Fair 1.553 0.4 poly styreneHEMA EGDM EGPEA 15 41% 26% 31% 2% 4.5 Poor Fair 1.552 3.1 poly styreneHEMA EGDM EGPEA 16 41% 27% 31% 1% 4.8 Poor Fair 1.549 4.6 poly styreneHEMA EGDM EGPEA 17 20% 40% 40% 1% 3.2 Good Poor 1.551 2.1 poly styreneHEMA EGDM EGPEA 18 41% 27% 31% 1% 5.1 Fair Fair 1.547 2.1 poly chloro-HEMA EGDM EGPEA styrene 19 40% 26% 30% 4% 4.2 Fair Fair 1.551 0.2 polychloro- HEMA EGDM EGPEA styrene

[0062] EWC Foldability Comparative (Weight After Expansion Material %)RI Machinability Hydration % Hydrogel 1 60 1.38 Good Good 15 Hydrogel 230 1.44 Good Good 11 Hydrogel 3 75 1.34 Good Good 25 Hydrogel 4 20 1.46Good Good 10 Acrylic 1  0 1.54 Not —  0 Machinable Acrylic 2  0 1.55 Not—  0 Machinable

[0063] In the above table, “machinability” refers to cutting theunhydrated material with a lathe in which a diamond tool comes incontact with the material while rotating at high speed. Goodmachinability means the material cuts cleanly into disks so the radiiand dimensions of the final product may be selected in advance. Fairmachinability means the material can be machined if environmentalparameters can be controlled, for example, by decreasing thetemperature. Poor machinability means the material tends to deform orbreak when lathe cut, but it is still machinable if environmentalparameters are controlled. Not machinable means the material cannot becut with a lathe and must be formed using methods such as molding.“Foldability” refers to the ability to bend the material as much asabout 180° without breaking once the material has been hydrated. Goodfoldability means the material can be easily folded using forceps whenthe material is cut into a disk about the size of a standard lens. Fairfoldability means a hydrated disk of the material folds when applyinglittle force. Poor foldability means the hydrated disk folds withoutbreaking when a greater force is applied.

Example 2

[0064] A hydration study was conducted to assess the change in dimensionafter complete hydration. Twenty samples of each formulation describedin Example 1 were used. Samples consisted of disks 16.5 mm in diameterand 2.0 mm in thickness. The results were averaged for each formulation.Formulation % Change in Diameter % Change in Thickness 1 0.02 ± 0.010.04 ± 0.01 2 0.05 ± 0.02 0.08 ± 0.02 3 0.06 ± 0.01 0.08 ± 0.01 4 0.08 ±0.03 0.06 ± 0.01

[0065] There were no significant dimensional changes after hydration.

What is claimed is:
 1. A hydratable copolymer comprising: a) a firstmonomeric component which comprises an aryl acrylate or an arylmethacrylate; b) a second monomeric component which comprises a monomerhaving an aromatic ring with a substituent having at least one site ofethylenic unsaturation, wherein the second monomeric component is otherthan an acrylate; and c) a third monomeric component which comprises ahigh water content hydrogel-forming monomer.
 2. The copolymer of claim 1wherein the copolymer becomes flexible when hydrated, and wherein thehydrated copolymer expands less than about 10 volume percent compared tothe unhydrated copolymer.
 3. The copolymer of claim 1 wherein thecopolymer becomes flexible when hydrated, and wherein the hydratedcopolymer has an equilibrium water concentration less than about 5weight percent.
 4. The copolymer of claim 1 wherein the copolymer isrigid at normal room temperature when dry, and flexible at normal roomtemperature when hydrated.
 5. The copolymer of claim 2 wherein thehydrated copolymer has a refractive index greater than about 1.50. 6.The copolymer of claim 2 wherein the unhydrated copolymer is machinableat normal room temperature.
 7. The copolymer of claim 1 wherein thecopolymer is for use in an ophthalmic device.
 8. The copolymer of claim7 wherein the ophthalmic device is an intraocular lens.
 9. The copolymerof claim 1 wherein the copolymer further comprises a crosslinking agent.10. The copolymer of claim 1 wherein the copolymer has a glasstransition temperature greater than about room temperature.
 11. Thecopolymer of claim 1 wherein the copolymer is machinable at normal roomtemperature and has a refractive index greater than about 1.50.
 12. Thecopolymer of claim 1 wherein the first monomeric component correspondsto the formula:

wherein: Z is —H or —CH₃, and Q is a substituent containing at least onearomatic ring.
 13. The copolymer of claim 12 wherein Q is selected fromthe group consisting of: ethylene glycol phenyl ether, poly(ethyleneglycol phenyl ether acrylate), phenyl, 2-ethylphenoxy, 2-ethylphenoxy,hexylphenoxy, hexylphenoxy, benzyl, 2-phenylethyl, 4-methylphenyl,4-methylbenzyl, 2-2-methyphenylethyl, 2-3-methylphenylethylmethacrylate, 24-methylphenylethyl, 2-(4-propylphenyl)ethyl,2-(4-(1-methylethyl)pheny)ethyl, 2-(4-methoxyphenyl)ethyl,2-(4-cyclohexylpheny)ethyl, 2-(2-chlorophenyl)ethyl,2-(3-chlorophenyl)ethyl, 2-(4-chlorophenyl)ethyl,2-(4-bromophenyl)ethyl, 2-(3-phenylphenyl)ethyl,2-(4-phenylphenyl)ethyl), and 2-(4-benzylphenyl)ethyl.
 14. The copolymerof claim 1 wherein the first monomeric component is selected from thegroup consisting of ethylene glycol phenyl ether acrylate, poly(ethyleneglycol phenyl ether acrylate), phenyl methacrylate, 2ethylphenoxymethacrylate, 2-ethylphenoxy acrylate, hexylphenoxy methacrylate,hexylphenoxy acrylate, benzyl methacrylate, 2-phenylethyl methacrylate,4-methylphenyl methacrylate, 4-methylbenzyl methacrylate,2-2-methyphenylethyl methacrylate, 2-3-methylphenylethyl methacrylate,2-4-methylphenylethyl methacrylate, 2-(4-propylphenyl)ethylmethacrylate, 2-(4-(1-methylethyl)pheny)ethyl methacrylate,2-(4-methoxyphenyl)ethylmethacrylate, 2-(4-cyclohexylpheny)ethylmethacrylate, 2-(2-chlorophenyl)ethyl methacrylate,2-(3-chlorophenyl)ethyl methacrylate, 2-(4-chlorophenyl)ethylmethacrylate, 2-(4-bromophenyl)ethyl methacrylate,2-(3-phenylphenyl)ethyl methacrylate, 2-(4-phenylphenyl)ethylmethacrylate), 2-(4-benzylphenyl)ethyl methacrylate, and mixturesthereof.
 15. The copolymer of claim 1 wherein the first monomericcomponent is selected from the group consisting of ethylene glycolphenyl ether acrylate and poly ethylene glycol phenyl ether acrylate.16. The copolymer of claim 1 wherein the copolymer includes at leastabout 10 weight percent of the first monomeric component.
 17. Thecopolymer of claim 1 wherein the second monomeric component includessubstituted styrene or unsubstituted styrene.
 18. The copolymer of claim1 wherein the second monomeric component is selected from the groupconsisting of styrene and styrene substituted with at least one halogen,lower alkyl or lower alkoxy substituent.
 19. The copolymer of claim 1wherein the second monomeric component is selected from the groupconsisting of styrene and chloro styrene.
 20. The copolymer of claim 1wherein the copolymer includes at least about 10 weight percent of thesecond monomeric component.
 21. The copolymer of claim 1 wherein thethird monomeric component includes a methacrylate without an aromaticsubstituent.
 22. The copolymer of claim 1 wherein the third monomericcomponent is selected from the group consisting of: hydroxyethylmethacrylate, hydroxyethoxyethyl methacrylate, hydroxydiethoxyethylmethacrylate, methoxyethyl methacrylate, methoxyethoxyethylmethacrylate, methoxydiethoxyethyl methacrylate, ethylene glycoldimethacrylate, n-vinyl-2-pyrrolidone, methacrylic acid, vinyl acetate,and mixtures thereof.
 23. The copolymer of claim 1 wherein the thirdmonomeric component is selected from the group consisting ofhydroxyethyl methacrylate, hydroxy ethoxyethyl methacrylate, andmethacrylic acid.
 24. The copolymer of claim 1 wherein the copolymerincludes at least about 10 weight percent of the third monomericcomponent.
 25. The copolymer of claim 9 wherein the crosslinking agentcomprises a diacrylate or a dimethacrylate.
 26. A hydratable copolymercomprising: a) at least about 20 weight percent of a first monomericcomponent selected from the group consisting of ethylene glycol phenylether acrylate, and polyethylene glycol phenyl ether acrylate; b) atleast about 10 weight percent of a second monomeric component selectedfrom the group consisting of substituted styrene and unsubstitutedstyrene; c) at least about 10 weight percent of a third monomericcomponent selected from the group consisting of hydroxy ethylmethacrylate, hydroxyethoxy ethyl methacrylate, and methacrylic acid;and d) less than about 10 weight percent of a crosslinking agentselected from the group consisting of a diacrylate and a dimethacrylate,wherein the copolymer has a refractive index greater than about 1.50,and is foldable at normal room temperature when hydrated.
 27. Thecopolymer of claim 26 wherein the crosslinking agent comprises ethyleneglycol dimethacrylate.
 28. The copolymer of claim 26 wherein the firstmonomeric component comprises polyethylene glycol phenyl ether acrylate,the second monomeric component comprises styrene, the third monomericcomponent comprises hydroxy ethyl methacrylate, and the crosslinkingagent comprises an ethylene glycol dimethacrylate.
 29. The copolymer ofclaim 26 wherein the copolymer comprises: a) less than about 50 weightpercent of the first monomeric component; b) less than about 40 weightpercent of the second monomeric component; c) less than about 60 weightpercent of the third monomeric component; and d) at least about 1 weightpercent of the crosslinking agent.
 30. The copolymer of claim 26 whereinthe copolymer comprises: a) from about 30 to about 45 weight percentethylene glycol phenyl ether acrylate, polyethylene glycol phenyl etheracrylate, or mixtures thereof; b) from about 20 to about 30 weightpercent styrene; c) from about 25 to about 40 weight percent hydroxyethyl methacrylate, hydroxy ethyl methacrylate, or mixtures thereof; andd) from about 1 to about 5 weight percent of the crosslinking agent. 31.An ophthalmic device comprising a hydratable copolymer, the copolymercomprising: a) at least about 20 weight percent of a first monomericcomponent selected from the group consisting of ethylene glycol phenylether acrylate, and polyethylene glycol phenyl ether acrylate; b) atleast about 10 weight percent of a second monomeric component selectedfrom the group consisting of substituted styrene and unsubstitutedstyrene; c) at least about 10 weight percent of a third monomericcomponent selected from the group consisting of hydroxy ethylmethacrylate, hydroxyethoxy ethyl methacrylate, and methacrylic acid;and d) less than about 10 weight percent of a crosslinking agentselected from the group consisting of a diacrylate and a dimethacrylate,wherein the copolymer has a refractive index greater than about 1.50 andis foldable at normal room temperature when hydrated.
 32. The ophthalmicdevice of claim 31 wherein the ophthalmic device is an intraocular lens.33. A method of manufacturing an intraocular lens, the methodcomprising: a) providing a rigid, hydratable copolymer comprising afirst monomeric component which comprises an aryl acrylate or an arylmethacrylate; a second monomeric component which comprises a monomerhaving an aromatic ring with a substituent having at least one site ofethylenic unsaturation, wherein the second monomeric component is otherthan an acrylate; and a third monomeric component which comprises a highwater content hydrogel-forming monomer, wherein the copolymer has aglass transition temperature greater than about normal room temperature;b) forming a rigid intraocular lens having the desired dimensions fromthe rigid copolymer; and c) hydrating the copolymer to form a foldable,hydrated intraocular lens, wherein the hydrated intraocular lens has anequilibrium water concentration less than about 10 weight percent, and arefractive index greater than about 1.55.
 34. The method of claim 33wherein the rigid intraocular lens and the foldable hydrated intraocularlens differ in volume by less than about 10%.
 35. The method of claim 33wherein the intraocular lens is a 20 diopter lens and has a centralthickness less than about 0.4 mm.
 36. The method of claim 33 wherein thecopolymer is hydrated by: placing the copolymer in an aqueous solution;gradually increasing the temperature of the aqueous solution to about40° C.; holding the temperature of the aqueous solution at about 40° C.for at least about 10 minutes; gradually increasing the temperature ofthe aqueous solution to about 60° C.; holding the temperature of theaqueous solution at about 60° C. for at least about one hour; andgradually decreasing the temperature of the aqueous solution to aboutroom temperature.
 37. The method of claim 33 wherein the rigidintraocular lens is formed by cutting a lens from a rigid sheet of thecopolymer, and polishing the lens.
 38. A method of implanting anophthalmic device within an eye, the method comprising: providing ahydratable ophthalmic device which is rigid at room temperature when dryand foldable at room temperature when hydrated, the hydratableophthalmic device being hydrated; providing a syringe containing thehydrated ophthalmic device; and injecting the ophthalmic device into theeye.
 39. The method of claim 38 wherein the ophthalmic device is anintraocular lens
 40. The method of claim 38 wherein the hydratableophthalmic device comprises a copolymer including: a) a first monomericcomponent which comprises an aryl acrylate or an aryl methacrylate; b) asecond monomeric component which comprises a monomer having an aromaticring with a substituent having at least one site of ethylenicunsaturation, wherein the second monomeric component is other than anacrylate; and c) a third monomeric component which comprises a highwater content hydrogel-forming monomer.
 41. The method of claim 38wherein the ophthalmic device is injected into the eye through anincision less than about 1 millimeter in length.
 42. A copolymer formedby the process comprising: a) mixing a first monomeric component, asecond monomeric component, a third monomeric component and acrosslinking agent to form a reaction mixture, wherein the firstmonomeric component comprises an aryl acrylate or an aryl methacrylate;the second monomeric component comprises a monomer having an aromaticring with a substituent having at least one site of ethylenicunsaturation, the second monomeric component being other than anacrylate; and the third monomeric component comprises a high watercontent hydrogel-forming monomer; and b) subjecting the reaction mixtureto polymerization conditions to form the copolymer.